Racial Differences in Optic Nerve Head (ONH) and Laminar Surface Compliance in Normal Human Subjects

Abstract

 

Purpose

 

To determine the demographic and ocular factors associated with change in cup depth (CD) and lamina cribrosa depth (LCD) resulting from acute IOP elevations in normal human subjects using Spectral Domain Ocular Coherence Tomography (SDOCT).

 

Methods

 

The ONHs of 21 patients were imaged with SDOCT at baseline and after IOP was raised ~15 mm Hg via ophthalmodynamometry for 1 minute. We compared CD and LCD from baseline to increased IOP as follows. Anatomic structures were delineated in 24 radial B-scans of the 48-scan OCT data set using custom software (Strouthidis et al., IOVS 2011). A plane containing the best-fit ellipse was computed using principal component analysis to define Bruch’s Membrane Opening (BMO), which was used as the anatomic measurement reference. A mesh was reconstructed from the point cloud for the anterior surface of lamina cribrosa (LC) and Internal Limiting Membrane (ILM). We then measured the distance from the BMO reference plane to the LC mesh and ILM on a uniform sampling grid to calculate the mean position of the LC surface (LCD) and the ILM (cup depth or CD). We analyzed the association of CD and LCD with increased IOP, age, CCT (central corneal thickness), and race (European Descent (ED) or African Descent (AD)).

 

Results

 

Significantly greater deepening of the ONH surface upon IOP elevation was independently associated with European heritage, the magnitude of IOP elevation, and thicker CCT. Change in LCD was not significant with any variable.

 

Conclusions

 

Individuals of African descent show reduced ONH surface compliance, while greater ONH surface compliance was seen with increasing IOP change and thicker CCT. No significant changes in laminar compliance were seen within SDOCT volumes with any factor.

 

 

Keywords: 629 optic nerve • 550 imaging/image analysis: clinical • 568 intraocular pressure